Various stain materials such as discharged materials from factories and automobiles, droppings of fouls, saps or pollens adhere to paint films such as paint films on outside plates of automobile, which are exposed with rain and wind in outdoor, so that the appearances are gradually damaged. Therefore, in order to maintain the initial appearance of the paint film, it is necessary to perform the maintenance such as washing at high frequency.
For the purpose to decrease the frequency of maintenance, a wax film has been formed on the paint film in recent years. A wax agent forming the wax film generally comprises a wax ingredient for forming the film and giving water repellency, a silicone ingredient for providing gloss and making the wiping out easy, and an organic solvent for functioning as solvent or dispersing medium of the ingredients. After the wax agent is applied on the paint film by sponge and the like, the wax film is formed by wiping out excess wax agent with soft cloth and the like and polishing up the paint film. But, though the wax film gives gloss to the paint film, the wax film is repellent so that rain drops containing stain materials contracts on the wax film. Therefore, the stain materials is condensed partially and when the rain water is dried, mottling is formed on the paint film of a horizontal plane and rain line traces are formed on the paint film of a vertical plane. Further, the wax film is softer than the paint film so that the adhered stain materials are buried in it and it is difficult to remove the stain materials by natural actions such as wind and rain. That is, even if the wax film is formed on the paint film, there are not actually effects to decrease the maintenance frequency.
For achieving the foregoing objects, a coating composition formulating a specific organosilicate and/or a condensate thereof in a specific organic coating composition was suggested(Publication of unexamined International Application WO 94/06870). Also , the present inventors suggested a thermosetting composition comprising a resin ingredient, a curing agent ingredient and a dispersion of inorganic sol (Publication of unexamined International Application WO 97/13809), for achieving the foregoing objects. And, the paint films obtained from the compositions have stain resistance because the organosilicate and/or a condensate thereof or the inorganic particle is oriented on the surface of paint film and the paint film is modified to hydrophilicity. Accordingly, the object to decrease the maintenance frequency is achieved. But, because the compositions are a invention on the assumption of industrial applications, the compositions contain usually large amount of the organic solvent and a special coating device is required in using the compositions. When a part of the paint films obtained from the compositions is cut deep for some reason, the organosilicate and/or a condensate thereof or the inorganic particle is dropped form the paint film surface according to circumstances, so that there are a problem that only the part is stained. So, a stainproof-treating agent and a method for stainproof-treating for repairing it easily are required.
For the objects, an outdoor article having a paint film surface of 102 or more in octane contact angle, which is obtained by applying a surface-treating agent comprising a silicon compound and a film-making ingredient of a fluororesin, was suggested (Japanese patent kokai publication hei 7-109435). However, the outdoor article is insufficient in stain resistance according to circumstances. Also, a coating agent for paint film, in which a powder of metal oxide having light catalytic action is mixed into a base material comprising a wax ingredient as main component, was suggested (Japanese patent kokai publication hei 9-220524). However, in order to form the film of the coating agent, working for wiping up excess coating agent and polishing the film are required after applying the coating agent on the paint film. Further, a stainproof-treating agent which can provide stain resistance to the substrate by simple working and a simple method for stainproof-treating are required.
The present invention accordingly has an object to provide a stainproof-treating agent, which can be applied on a substrate without requiring a special device, can provide stain resistance to the substrate by modifying the surface of the substrate hydrophilic according to simple working, and can decrease easily the frequency of maintenance such as washing, a simple method for stainproof-treating performed by using the stainproof-treating agent and a stainproof-treated article treated by the method for stainproof-treating.
Extensive investigations undertaken by the present inventors with the objects described above lead to a discovery that the objects can be achieved by a stainproof-treating agent: which comprises (A) a specific resin ingredient, (B) a specific oxide sol ingredient, (c) an organic solvent and (D) water in specific formulation ratio.